Centrifuge and method for neutralizing fatty oils



March 24,1959 |;'A.Al -'ZEL lUS 2,879,282

CENTRIFUGE AND METHOD FOR NEUTRALIZINGVFATTY OILS Filed June 10, 1954 gmllll 5 a a Y 5 g i INVENTOR IVAR AXEL AFZELVIUS ATTORNEYS United States Patent CENTRIFUGE AND METHOD FOR NEUTRALIZING FATTY OILS Ivar Axel Afzelius, Bromma, Sweden, assignor to Aktiebolaget Separator, Stockholm, Sweden, a corporation of Sweden Application June 10, 1954, Serial No. 435,847 Claims priority, application Sweden June 13, 1953 4.Claims. Cl. 260-425) This invention relates to the refining of fatty oils, such as oils of vegetable, animal or fish origin, and has particular reference to an improved method and apparatus for neutralizing such oils.

It has been proposed heretofore (for example, in Clayton Patent No. 2,182,755, issued December 5, 1939) to neutralize fatty oils by leading separate streams of oil and alkali to a centrifugal separator and mixing them with each other directly in the entrance of the centrifuge. For this purpose an open centrifuge disclosed in Clayton Patent No. 2,100,277 has been proposed. The oil and the alkali are introduced into this centrifuge from above through an inlet in the form of a stationary tube and then fall downward toward the rotor bottom. Here they meet rotating surfaces and are rapidly mixed with each other, the alkali solution and the soap formed being separated immediately from the oil. A more thorough separation of the oil takes place in the separating chamber into which the oil-alkali mixture is fed under the influence of the centrifugal force.

As is known, mixtures of soap and fatty oil have astrong tendency to form emulsions. The formation of emulsion is furthered by a violent agitation of the soap-oil mixture, as occurs with a strong shock effect when oil, lye and the soap formed are set in rapid rotation at the rotor bottom according to the method described above. Since emulsion formation, in turn, causes oil losses by the fact that oil is emulsified into the soap Patented Mar. 24, 1959 2 which may form the rotating chamber mentioned above and which is kept filled with oil. From the hollow spindle, the mixture obtained is then fed into the separating chamber.

It has been found that the injection of lye will give better results (i. e., lower neutralization losses). if it is done radially into the rotating chamber. The results will be even better if the injection is carried out in the rotating chamber at a point spaced from its inlet end, that is, at a point where acertain speed of rotation has been imparted to the oil. Both of these last mentioned measures have in fact been found to counteract emulsion formation.

The invention further comprises a centrifugal separator having a vertical axis of rotation and a hollow spindle 7 leading upward toward the separating chamber proper and in the lower part of which .two hermetically closed inlets (in the form of concentric tubes) for oil and alka line reagent, respectively,are arranged, the inlet for the alkaline reagent being the inner one. The hollow spindle communicates with the separating chamber, and the latter has separate outlets for oil and soap. This separator is characterized principally in that the inlet for the alkaline reagent has outlet holes which open radially into the hollow spindle.

The invention is described in more detail below, referend: being made to the attached drawing in which Fig. 1

and is lost with the soap, it is always desirable in the her in a centrifugal separator, while keeping the rotating chamber filled with oil, so that the alkaline reagent is led directly into and mixed with the oil mass which fills and rotates with this chamber, and then leading the resulting mixture into the separating chamber of the separator and there dividing it into oil and soap which are discharged through separate outlets. This avoids the strong shock effect at that moment when the lye is mixed with the oil, so that the risk of emulsion formation is removed or at least greatly reduced and a sufiicient reaction time is attained. This method also avoids mixing of air into the oil, which would cause the soap particles to take up air bubbles and thus become lighter so that they would be separated with the oil and'contaminate it. Furthermore, the oxidizing effect of the air on the oil is eliminated in this way.

In the practice of the method, a so-called hermetically closed separator can be used, and the oil and the alkaline reagent may be fed from below through a hollow spindle is a vertical sectional view of a centrifugal separator having hermetically closed inlets, and Fig. 2 is a vertical sectional view on a larger scale showing the orifice end of the inlet for the alkaline reagent.

Referring to the drawing, the inlet for the oil' is formed by a stationary tube 1, and the inlet for the alkaline reagent (hereinafter called lye) is formed by a stationary tube 2 which extends into the tube 1 and is surrounded by the latter. The oil passing upward through tube 1 enters the annular space 3 between the inside of a hollow spindle 4 and the upperend portion 5 of the lye tube 2. The hollow of the spindle forms a feed chamber 4a rotating with and leading upward to a centrifugal bowl B, as will be described in greater detail presently:

At its lower end portion, the spindle 4 is surrounded by a stationary sealing device 4b connected to the upper end portion of oil supply tube 1. This sealing device constitutes a means forming an hermetically sealed passage between the fixed tube 1 and the lower portion of the bowl spindle. Since sealing devices for this purpose are well-known in the centrifugal art, no further descrip tion of the sealing device 4b is needed. The lye tube 2 extends upward into the hollow spindle for a sub-' stantial distance and, as shown in Fig. 2', its upper end' portion 5 has outlet holes 6 in the side wall of the tube. Thus, the outlet holes 6 open radially into the feed chamber 4a at a region well above the lower end of .the spindle and the hermetic passage-forming means 46.

At its upper end, the spindle chamber 4a communi cates through holes'7 with channels 8 in the centrifugal bowl B. These channels lead to the distributing holes 9' in a set of spaced conical discs'10, the spaces between these discs forming a centrifugal separating chamber or. locus of centrifugal force. Located radially inward from this separating chamber is an upwardly extending channel 11 forming an oil outlet. An annular chamber 12 is located between the outer edges of the discs 10 and the L cover 15 of the bowl and its top disc 16. The oil and soap are removed from the bowl outlets 11- and. 14,. respectively, in any conventional manner, as by means of pipes having sealedflow connections (not shown), with the respective outlets.

It will be understood, that the oil and' reagent are fed from below, n erum: st eams underp c m' into th rotating spindle chamber 4a of the centrifugal locus formed by the rotating bowl B and its depending spindle, thes streams passingto the spindlechamber by way of theoil passage between the tubes 1 and 2, and the reagent passage within the tube 2. The bowl may be driven from a suitable motor (not shown) connected to the spindle intermediate its ends. During this feeding, the rotating chamber 4a is kept filled with oil, so that the reagent is led directly into and mixed with the oil mass rotating with and filling this chamber. The reagent is injected into this surrounding .mass in the radial direction of the rotating chamber 4a, by way of the holes 6 which are located at a region beyond the points where the oil enters the chamber 411, reckoned in the direction of flow through the chamber.

.From the hollow spindle 4, the oil (which new contains soap) is passed to the separating locus containing the discs 10. This passage of the oil-soap mixture occursduring the feeding of fresh oil and reagent to the rotating chamber 4a and while continuing to impart rotation to the mixture incident to its flow through the rotating holes 7 and channels 8. The separation of the oil takes place centrifugally in the spaces between the discs, the oil discharging upward and inward through channel 11. The soap flows radially outward to the annular chamber 12 and discharges through channel 14.

The practice of the method according to the invention is illustrated in the following examples, in all of which the oil is introduced into the mixing device at a temperature of 85 C., and caustic soda lye of 20 B. and room temperature is used as neutralization agent in a quantity exceeding by 25% that quantity which is theoretically required for the neutralization of the fatty acids.

Example 1 Palm oil with a free fatty acid content of 5.0% is neutralized by the method disclosed in said Patent No. 2,182,755. The oil leaving the centrifuge has a free fatty acid content of 0.40%, which value, however, is unallowably high. The neutralization loss (i.e. the quantitative difference between the neutralized and unneutralized oil) is 7.2%

According to another known method, the oil and the lye are mixed in a rotating disc mixer (the oil and the lye are each led in a stream toward a disc rotating in a mixing chamber) and the mixture is then separated in a centrifuge having an hermeticallyclosed inlet; A neutralizationiloss of 8.5% and a free fatty acid content of -IQ6%yin the neutralized oil 'are obtained.

when the same oil is neutralized by the method of the present invention, a neutralization loss of only 6.3% and a free fatty acid content of 0.07% are obtained.

Example 2 Example 3 Cottonseed oil having a free fatty acid content of 5.0% i

is neutralized in said disc mixer, and after separation a neutralization loss of 8.8% and a free fatty acid content of 0.04% in theneutralized oil are obtained.

When neutralizing this oil according to theinvention, aneutralization loss of 7.4% and afree. fatty acid content or 0.04%. in the neutralized .oil. are ob ained.

Example 4 Rapeseed oil having a free fatty acid content of 2.3% is neutralized in said disc mixer, and after separation a neutralization loss of 3.7% and a free fatty acid content of 0.04% in the neutralized oil are obtained.

When using the present method to neutralize this oil, a neutralization loss of 3.2% and a free fatty acid content t of 0.05% in the neutralized oil are obtained.

Example 5 Peanut oil having a free fatty acid content of 2.8% is neutralized in said disc mixer, and after separation a neutralization loss of 4.2% and a free fatty acid content of 0.04% in the neutralized oil are obtained.

When proceeding according to the present invention, a neutralization loss of 3.6% and a free fatty acid content of 0.04% in the neutralized oil are obtained.

As appears from the examples given above, the neutralization loss is reduced with the new method as compared with that given in the known methods, and a satisfactorily low content of free fatty acids is obtained in the neutralized and separated oil. The favorable result with the new method seems to depend upon the fact that the soap formed, when mixing the lye and the oil, is rapidly separated out even in themixing chamber (the rotating chamber filled with oil) owing to the centrifugal force, and accumulates at the wall of the chamber, from which it flows with little or no disturbance into the separating chamber of the separator. In this way, a minimum of neutral oil will be occluded in the soap, which means that the oil losses will be small. The short time during which oil and lye are in contact with each other counteracts losses by saponification of neutral oil but is suflieient to neutralize satisfactorily the free fatty acids of the oil.

For illustrative purposes I have described the invention in connection with the use of a neutralizing agent which has a saponifying efiect, so that soap is formed incident to neutralizing the free fatty acids in the oil. It will be understood, however, that other neutralizing agents may be employed instead, such as soda ash or the ammonia derivatives sometimes used in refining oils of this type, to neutralize the free fatty acids. Regardless of the particular neutralizing agent which is fed to the oil through the reagent tube 2, there will be some preliminary separation of neutralization products in the mixing chamber 4a, and the relatively undisturbed flow from this chamber into the bowl B (where the final separation of the neutralization products occurs) will prevent any substantial occlusion of oil in the neutralization products.

I claim:

1. In a centrifuge for use in treating fatty oils with a neutralizing reagent, including a centrifugal bowl rotatable on a vertical axis and having a separating chamber provided with separate outlets for oil and neutralization products, and a hollow spindle depending from the bowl and forming a rotating feed chamber communicating with the separating chamber, the improvement which comprises a reagent supply tube fixed at the lower end of the spindle and projecting upward into the feed chamber, an oil supply tube fixed in surrounding relation to said first tube and forming therewith an oil passage, and means forming an hermetically sealed passage between the oil supply tube and the lower portion of the bowl spindle, said reagent tube having outlet holes opening radially into the spindle at points located beyond said passage forming means, reckoned in the direction of oil flow through said last means and the spindle.

2. The improvement according to claim 1, in which said outlet holes in the reagent tube open radially into the. spindle at a region above said hermetic passage-forming means.

3. In the neutralizing of fatty oils by means of an alkaline reagent, theimprovement which comprises feed ing separate. streams of'the oil and reagent, respectively;

into a rotating chamber of a centrifugal locus, keeping said chamber completely filled with oil during said feeding, the reagent being injected directly into and mixed with the oil mass rotating with and filling said chamber, said injection of the reagent into the oil in the rotating chamber being at a region thereof located beyond the point where the oil enters said chamber, reckoned in the direction of flow through the chamber, passing the resulting mixture directly from said chamber into a separating chamber of said locus and there centrifuging the mixture to divide it into oil and soap, and separately discharging the oil and soap from said locus.

4. The improvement according to claim 3, in which the reagent is injected into the oil in the radial direction of the rotating chamber.

6 References Cited in the file of this patent UNITED STATES PATENTS Jones Mar. 2, 1926 Svensjo Aug. 3, 1937 Ayres et al Nov. 29, 1938 Clayton et al.- Dec. 5, 1939 Froding Feb. 4, 1941 Ayres Dec. 22, 1953 FOREIGN PATENTS Germany May 16, 1936 

1. IN A CENTRIFUGE FOR USE IN TREATING FATTY OILS WITH A NEUTRALIZING REAGENT, INCLUDING A CEENTRIFUGAL BOWL ROTATABLE ON A VERTICAL AXIS AND HAVING A SEPARATING CHAMBER PROVIDED WITH SEPARATE OUTLETS FOR OIL AND NEUTRALIZATION PRODUCTS, AND A HOLLOW SPINDLE DEPENDING FROM THE BOWL AND FORMING A ROTATING FEED CHAMBER COMMUNICATING WITH THE SEPARATING CHAMBER, THE IMPROVEMENT WHICH COMPRISES A REAGENT SUPPLY TUBE FIXED AT THE LOWER END OF THE SPINDLE AND PROJECTING UPWARD INTO THE FEED CHAMBER, AN OIL SUPPLY TUBE FIXED IN SURROUNDING RELATION TO SAID FIRST TUBE AND FORMING THEREWITH AN OIL PASSAGE, AND MEANS FORMING AN HERMETICALLY SEALED PASSAGE BETWEEN THE OIL SUPPLY REAGENT TUBE AND THE LOWER PORTION OF THE BOWL SPINDLE, SAID REAGENT TUBE HAVING OUTLET HOLES OPENING RADIALLY INTO THE SPINDLE AT POINTS LOCATED BEYOND SAID PASSAGE FORMING MEANS, RECKONED IN THE DIRECTION OF OIL FLOW THROUGH SAID LAST MEANS AND THE SPINDLE.
 3. IN THE NEUTRALIZING OF FATTY OILS BY MEANS OF AN ALKALINE REAGENT, THE IMPROVEMENT WHICH COMPRISES FEEDING SEPARATE STREAMS OF THE OIL AND REAGENT, RESPECTIVELY, INTO A ROTATING CHAMBER OF A CENTRIFUGAL LOCUS, KEEPING SAID CHAMBER COMPLETELY FILLED WITH OIL DURING SAID FEEDING, THE REAGENT BEING INJECTED DIRECTLY INTO AND MIXED WITH THE OIL MASS ROTATING WITH AND FILLING SAID CHAMBER, SAID INJECTION OF THE REAGENT INTO THE OIL IN THE ROTATING CHAMBER BEING AT A REGION THEREOF LOCATED BEYOND THE POINT WHERE THE OIL ENTERS SAID CHAMBER, RECKONED IN THE DIRECTION OF FLOW THROUGH THE CHAMBER, PASSING THE RESULTING MIXTURE DIRECTLY FROM SAID CHAMBER INTO A SEPARATING CHAMBER OF SAID LOCUS SAND THERE CENTRIFUGING THE MIXTURE TO DIVIDE IT INTO OIL AND SOAP, AND SEPARATELY DISCHARGING THE OIL AND SOAP FROM SAID LOCUS. 